Nonpolar ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{N}/\mathrm{GaN}\left(11\mathrm{}¯00\right)$ multiple quantum wells grown on $\gamma -{\mathrm{LiAlO}}_2\mathrm{}\left(100\right)\mathrm{}$ by plasma-assisted molecular-beam epitaxy

$M$-plane ${\mathrm{In}}_{0.1}{\mathrm{Ga}}_{0.9}\mathrm{N}\left(11\mathrm{}¯00\right)$ multiple quantum wells were grown on $\gamma -{\mathrm{LiAlO}}_2\mathrm{}\left(100\right)\mathrm{}$ by plasma-assisted molecular-beam epitaxy. The high brightness of the photoluminescence of these multiple quantum wells and the observation of band-edge emission from the barriers are consistent with the expected absence of spontaneous and piezoelectric polarization fields along the growth direction. Despite this fact, the recombination dynamics observed is rather complex and is shown to originate from the superposition of exciton relaxation towards a band of localized states and simultaneous recombination.